Multiple impregnation of compressible fibrous webs



Oct. 1,1, 1.938. M, Q SCHUR v (132,863l

UULTIPLE IKPREGNATION OF COMPRESSIBLE FIBROUS WEBS Filed Aug. 4, 1936 Patented Qt.11,193s A' y2,132,863

MULTIPLE mrPnEGNA'noN oF commiss- TBLE minous AwEns Milton 0. Schur, Berlin, N. H., assignor to Brown Corirlpany, Berlin, N. H., a corporation of Ma e Application August 4, 1936, Serial No. 94,156

Claims. (Cl. 91-68) This invention relates to multiple. impregna.- portunity of recovering part 'or much of its tion of a compressible fibrous web, that is, to the original thickness.

impregnation of such a web with different im- In the accompanying drawing,- pregnants or with different amounts or con- 4 Figure 1 illustrates diagrammatically and con- 5 centrations of the same impregnant at dierent ventionally the practice of a method embodying 5 portions of the depth or body of vthe `web. the present invention.

It is sometimes the practice to produce im- Figures 2, 3, and 4, represent sections through pregnated brous webs or sheets of the foregoing typical multiply-impregnated products such as character by superimposing and bonding tomight be produced by such method.

gether two or more plies each impregnated with As appears in Figure 1, a web or sheet S of 10 the desired material or to the desired impregcompressible fibrous material may be progresnant concentration. Not only is the impregnasively unwound from a roll R. and passed through tion of individual plies and their bonding or plya bath B of primary liquid binder such as may ing unduly expensive in some cases, but it is be desired in the main body portion of the web.

l5 sometimes diicult to work with thin plies, for As the impregnated web comes from the bath, 15 instance, thin paper plies such as are to be. imit may enter the nip of a pair of squeeze rolls C pregnated with aqueous binder compositions and whose peripheries clear each other by a gap to serve as surface layers in the finished plied Slightly IESS, fOr instance afbOllt -003 t0 -006 product. inch, than that of the thickness of the orig- In accordance with the present invention, I inal or dry web, which may `have an original 20 produce from a compressible single fibrous web thickness of, say, about 0.030 to 0.060 inch and an impregnated sheet Whose surface portion is which 4may swell or expand somewhat as a reimpregnated with a different material or con-, sult of impregnation with the primary liquid centration of the same material than the inbinder. The squeezed web may then be passed terior portion or layer of the sheet. A practice into contact with a lm of secondary liquid 25 embodying the invention hereof may, for exbinder on the periphery of a kiss roll K rotatample, involve passing a compressible fibrous ing partially submerged in a bath of the secweb or foundation through a bath of impregnatondary liquid binder L, whereupon the multiing liquid binder, then subjecting the wet imply-impregnated web may undergo such further pregnated web to light mechanical squeezing, as treatment as is necessary to cause the two binder 30 by passage through squeeze rolls, and then passcompositions therein to set or congeal. ing the squeezed wet web over a kiss or appli- By the foregoing method, it is possible, for cator roll rotating partially submerged in aninstance, to impregnate the body of a felted other or secondary liquid binder which it is iibrous web throughout with'rubber latex as the desired to incorporate into the surface portion primary impregnant, then to drive or dislodge 35 of the web. Because the wet impregnatedweb the rubber latex to a greater or lesser degree has been slightly squeezed, it is capable of imfrom the surface portions of the web by squeeze `bibing the secondary liquid binder and does so rolls, and then to replace the dislodged rubber immediately upon being brought into contact latex with aqueous albuminous binder, for in- 40 with the lm of liquid binder on the kiss roll. stance, glue solution. The resulting multiply- 40 The infusion of the secondary liquid binder into impregnated web may then be dried, as ,by the web preferably takes place promptly after passage throughahot-air drying chamber or over the squeezing of the web so as to avoid unsteam-heated drum driers. The resulting proddesirable setting of the first liquid binder in the uct thus impregnated mainly with rubber but surface portion of the web as the squeezed web comprising a surface portion impregnated with 45 tends to recover its original thickness. The apglue, which is shown in Figure 2, is of value plication of secondary liquid binder to the web as artificial leather for shoe innersoles and may, however, be delayed slightly after the other uses wherein it is desired that the artificial squeezing of the web in those instances when leather surface be substantially devoid of rubthe primary liquid binder does not tend to set bery feel. 50

or congeal rapidly; and; in such latter case, the Rather than incorporating aqueous albumiamount of secondary binder thatV can be added nous binder as a secondary binder into the surto the web is greater than when such binder face portion of the wet impregnated web after is infused into the web immediately after its its squeezing, I may employ glycerine as a secsqueezing, that is, before the web has had opondary impregnant, for instance, when a iln- 55 .viscous glycerine or glycerine solution is so greatly retarted that the rubber particles are set vbefore much diffusion has occurred.

In some instances, it may be desirable to produce an impregnated brous sheet of comparatively low rubber content in its main body portion but rich in rubber in its surface layer or portion, as when the surface is to be finished with nitrocellulose or other lacquer or liquid nish and loss or absorption of the finish in the body of the sheet is to be avoided. In Asuch cases, the main body of the brous web may be impregnated as a whole with a relatively dilute latex compositionand then, after the impregnated Web has been squeezed, its surface portion may be made to imbibe a' comparatively concentrated latex composition, namely, one which upon drying of the multiply-impregnated web' deposits sufilcient rubber and other solids the surface layer or portion to clog tc a desirable degree the pores and interstices in such layer. against material influx of such liquid nish as may be subsequently applied thereto.

Inproclucing the various multiply-impregnated products hereinbefore described for purpose of illustration, it is possible to work successfully with the compressible absorptive brous bases or webs fabricated from cellulose pulp; for instance, wood pulp, rag pulp, and other ber furnishes on papermaking machines. Of course, carded webs or felts' fabricated from cotton, wool, and other textile fibers, compressible woven cloths, and other compressible fibrous fabrics might serve as the foundations or basesbeing impregnated.

I claim:

1. A method which comprises impregnating substantially throughout its body with an aqueous impregnating composition a cellulose ber web tending to swell upon impregnation with such composition but being compressible to less than its original thickness, compressing the resulting impregnated and swollen web to less thanthew original web thickness and thereby dislodging aqueous impregnating composition from its surface portion, and infusing secondary liquid impregnant substantially only into said surface p0rtion While the web is still recovering from its compressed condition and it is still Wet with said aqueous impregnating composition.

2. A method which comprises progressively passing through a bath of aqueous impregnating composition a felted cellulose ber sheet tending to swell upon immersion in and impregnation with said composition but being compressible to less than its original thickness, progressively compressing the resulting swollen and impregnated sheet, as it emerges from said bath, to less than the original sheet thickness and thereby dislodging aqueous impregnating composition from its surface portion, and progressively applying secondary liquid impregnant as a coating to the surface ofsaid compressed sheet while it is still recovering from its compressed condition and it is still wet with said aqueous impregnating composition.

3. A method which comprises impregnating substantially throughout its body with rubber latex composition a cellulose flber web tending to swell upon impregnation with such composition but being compressible to less than its original thickness, compressing the resulting impregnated and swollen web to 'less than the original web thickness and thereby dislodging rubber latex composition from its surface portion, and infusing a secondary liquid impregnant substantially only into said surface portion while the web is still recovering from its compressed condition and it is still wet with said rubber. latex composition.

4. A method which comprises progressively passing through a bath of rubber latex composition a felted cellulose fiber sheet tending to swell upon immersion in and impregnation with said composition but being compressible to less than its original thickness, progressively compressingA the resulting swollen and impregnated sheet, as it emerges fromsaid bath, to less than the original sheet thickness and thereby dislodging rubber latex composition from its surface portion, and progressively applying aqueous albuminous binder composition as coatlng to the surface of said compressed sheet while it ls still recovering from its compressed condition and it is still wet with vsaid rubber latex composition.

5. A method which comprises progressively passing through a bath of relatively dilute rubber latex composition a felted cellulose ber sheet tending to swell upon immersion in and impregnation with said composltion but being compressible to less than its original thickness, progressively squeezing the' resulting swollen and impregnated sheet, as it emerges from said bath,` to less than the original sheet thickness and thereby dislodging rubber latex composition from its surface por-o tion, and progressively applying a relatively concentrated rubber latex composition as a coating to the surface of said compressed sheet while it is still recovering from its compressed condition and it is still wet with said relatively dilute rubber latex composition.

MILTON 0. SCHUR. 

